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  1. #1
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    Help!

    Hi guys, please help me with these two questions:

    Find the speed in m/s of a point on a bicycle rim of diameter 88 cm, making 200 revolutions per minute.

    and

    Eight tins of paint are required for a surface of an area 50 m{square} if 4 coats of paint are applied. Find the number of tins of paint needed for an area of 70 m{square} if 5 coats of paint are applied.
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  2. #2
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    Quote Originally Posted by laser2302
    Hi guys, please help me with these two questions:

    Find the speed in m/s of a point on a bicycle rim of diameter 88 cm, making 200 revolutions per minute.
    What you need to find first, is what is the circumference of the rim, which is $\displaystyle 88\pi$

    Now you need to find how many revolutions per second the rim goes, which is the amount rpm divide by 60 $\displaystyle 200\div60=3\frac{1}{3}$

    now we multiply the circumference by the rps and we get the answer...

    $\displaystyle 88\pi\times3\frac{1}{3}$ that gives us cm/s so we divide by 100 to get m/s

    $\displaystyle \frac{88\pi\times3\frac{1}{3}}{100}$ and that is the answer in m/s (I don't have a calc. handy so you need to solve)
    Quote Originally Posted by laser2302
    and

    Eight tins of paint are required for a surface of an area 50 m{square} if 4 coats of paint are applied. Find the number of tins of paint needed for an area of 70 m{square} if 5 coats of paint are applied.
    If 8tins are required for 4 coats, than only 2 tins are required for 1 coat. If 2 tins are required to cover 50m^2, than 1 tin will cover 25m^2.

    Now we need to figure out how many tins are required to cover 70m^2 with 1 coat. So we divide 70 by 25, $\displaystyle 70m^2\div25m^2=2\frac{2}{5}$

    so 2 and 2/5 tins are required for 1 coat, so now we multiply by 5 to get all 5 coats.

    $\displaystyle 2\frac{2}{5}\times5=12$ therefore, 12 tins are needed.
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